After more than 20 years in business, MercBar, a staple of SoHo social life, is closing, its owner said on Monday

Owner John McDonald planned to make Monday the last evening at the 2,000-square-foot bar, which he opened in February 1993 with the architect Campion Platt, fresh from graduating Columbia University the year prior.

Originally, Mr. McDonald leased the building—what he described as a single-story “shared wall structure” with a mezzanine—from Mr. Platt and Andre Balazs, who were constructing the Mercer Hotel at the time and parked their cars in the space. (He bought out Mr. Platt more than a decade ago and purchased the building in the last five years.)

The vision for MercBar was modeled, in part, after a lodge the fashion photographer Bruce Weber kept in the Adirondacks. Even now, that vision holds, with barn wood lining the walls and a canoe hanging above the bar.

From the get-go, MercBar attracted a fashion crowd, said Mr. McDonald, thanks to Mr. Balazs’s relationship with Katie Ford, the former CEO of Ford models, and Mr. McDonald’s own connections in Manhattan nightlife.

At the time, he explained, “most of going out involved big clubs. This was a small boutique, with no sign.” He added that the philosophy of MercBar never changed over the years: “We were open seven days a week, no DJs, no promoters, no drink specials, no mirrors, no TV set. Even though everything has been reupholstered 15 times and the carpets change, it’s always remained a time machine.”

Although fashion people, model bookers and photographers who worked in SoHo still flocked to MercBar for after-work drinks over the years, it attracted a broader audience, like “anything that’s very busy long-term does,” Mr. McDonald said. “For true longevity and a viable business, the crowd you always want is busy.”

Mr. McDonald, who operates two other restaurants that bookend Mercer Street, said he wasn’t closing the bar because of a lack of popularity. “On Saturday, it was as busy as it’s ever been,” he noted. But, as with most old buildings, the infrastructure is giving way, slowly. The floors are sinking and the walls are cracking. He has some ideas of what to do with the space, but he explained, “I’ve got to get through this mental chapter first.”

Having passed the two-decade mark, it seemed like a good time to call it quits. “I just had to pick a day,” he said. “I didn’t want there to be too much build-up. It’s drawing a line in the sand. For a lot of reasons you have to learn how to say goodbye to time versus letting it drag out.”

- Marshall Heyman